The invention relates to digital pulse generators for sequential firing of thyristors as can be used in static power converters.
With the use of thyristors and the adjunct control techniques, solid state technology and digital treatment of the operative modes have received extensive applications. In particular, as shown in copending patent application Ser. No. 845,741, filed on Oct. 26, 1977 by Gary E. Baumgart for "Translator Module For Interfacing A Sequence Controller With A Remote Source Of Logic Command Signals And Universal Modular Load Control Apparatus Embodying Such Sequence Controller And Translator Module", solid state technology and digital techniques have led to a modular organization of the entire power and control system, for instance, in the designing and manufacturing of a variable voltage and variable frequency static motor drive. In particular, the digital pulse generator igniting in sequence the thyristors of such a motor drive has been conceived as a module which can be added or assembled with other modules, and that can be adjusted and controlled in situ from an operator's panel. Modularization requires a careful selection of solid state components and a compact design. All this tends to facilitate the manufacture of a standard product having improved and well established characteristics at the lowest cost.
The object of the present invention is to provide an improved digital end-stop determination and control in a thyristor gating generator.
The technique for end-stop control is generally described in Chapter 10, pages 259 to 271 of "Thyristor Phase-Controlled Converters and Cycloconverters" of B. R. Pelly (Wiley-Interscience 1971). End-Stop control is intended to insure that firing the "next" thyristor in accordance with a reference signal and timing wave will not occur at a firing angle situated outside the permissible firing angle range, e.g. the range defined by a first (or advanced) end-stop (ES.sub.1) and a second (or retarded) end-stop (ES.sub.2). The first end-stop (ES.sub.1) blocks the generation of any early igniting pulse until the lower limit ES.sub.1 has been reached and then generates a gate firing pulse. The second end-stop (ES.sub.2) causes a gate firing pulse to occur when the comparator is late in providing the expected firing angle. One such technique has been shown in U.S. Pat. No. 4,028,609 of Richard L. Detering.
The object of the present invention is to provide an improved design, with increased reliability of operation and reduced manufacturing cost. In particular, LSI modular manufacture is more extensively used in the solid state circuitry, uniting on a common chip a maximum number of functions, and gate pulse suppression is also included thereon.